Níveis de fósforo disponível em rações para frangos de corte machos de 8 a 42 dias de idade mantidos em diferentes ambientes térmicos

• Autor(a) principal: Maia, Ana Paula de Assis
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5625
• topic: Ambiente térmico; Fósforo; Frangos; thermal environment; Phosphorous; Broilers; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PRODUCAO ANIMAL

A total of two thousand and forty male broilers of Cobb stain were used in four experiments to evaluate available phosphorous (AP) levels in diet for broilers from 8 to 42 days of age kept in high temperature and thermoneutral environment. In each experiment, the birds were distributed in a complete randomized experimental design in a 5 x 2 factorial scheme (five AP levels and two thermal environments: high temperature and thermoneutral). The trials were divided in two periods, from 8 to 21 days and 22 to 42 days of age. In both periods, it two tests were conducted, one to assessing the performance and bone parameters of broilers and other to determine the phosphorous excreted and retention of birds. In the period from 8 to 21 days, nine and eight repetitions with ten and five birds per repetition were used for the experiment 1 and 2, respectively. The AP levels obtained were: 0.25; 0.33; 0.41; 0.49 e 0.57%. The birds were brooded in controlled-environment rooms at 35ºC (high temperature) and 29ºC from 8 to 15 days and 27ºC from 16 to 21 days (thermoneutral environment). In the period from 22 to 42 days, nine and eight repetitions with six and five birds per repetition were used for the experiment 1 and 2, respectively. The AP levels obtained were: 0.25; 0.35; 0.45; 0.55 e 0.65%. The birds were brooded in controlled- environment rooms at 32ºC (high temperature) and 22ºC (thermoneutral environment). In the first phase, the levels of AP influenced the feed intake (FI) and weight gain (WG) which increased in a quadratic form up to the estimated level of 0.46%, for thermoneutral and heat environments, however, the LRP model better adjusted to data, where the 0.34 and 0.35% AP levels were estimated, for both thermal environments, respectively. In thermoneutral environment, the feed conversion ratio (FCR) improved in a quadratic way with the increase of AP levels until the estimated level of 0.45%, but, the LRP model better adjusted to data estimated at 0.34% the AP level. FCR of birds challenged by heat was not significantly effect by the levels of AP It was observed a quadratic effect of the treatments on the % of calcium and phosphorus in the bone (CaB and PB) which increased, respectively, up to the estimated levels of 0.46 and 0.47% of AP in both environments. In thermoneutral environment, it was observed a quadratic effect of the AP levels on phosphorous excreted (PE) which decreased up to the estimated level of 0.29% and on phosphorous retention (PR) and phosphorous retention coefficient (PRC) that increased up to the estimated levels of 0.54 and 0.40%, respectively. In heat stress the treatments have influenced the PE and PR in a linear form. The PRC increased in a quadratic form, with the increase of th AP levels, until the estimated level of 0.38%. In the period from 22 to 42 days of age, in high temperature environmental, it was observed a quadratic effect of the AP levels on FI, WG and FCR which improved until the estimated level of 0.46%. In thermoneutral environment, the treatments influenced the FI and WG that decreased in a linear form. It was not observed effect on FCR. Under thermoneutral conditions, there was a significant quadratic effect of AP levels on the % PB which increased up to the estimated level of 0.51% of AP. Under heat stress, the AP levels influenced in a quadratic form the % of CaB and PB in the bone that rose, respectively, until the estimated levels of 0.48 e 0.55% of AP. Irrespective of thermal environment, the treatments influenced the PE and PR that increased in a linear form, while PRC decreased in function of AP levels. It was concluded the estimated levels, respectively, 0.35 and 0.47% of AP provided the better results of performance and bone parameters of broilers from 8 to 21 days of age kept in thermoneutral and high temperature environment. From 22 to 42 days of age, AP requirements for broilers kept in thermoneutral and high temperature environment are, respectively, 0.25 and 0.46% of AP for maximum performance and 0.51% and 0.55% of AP for higher bone mineralization.